please answer as soon as it's possible,thx.
In a car? A garage door? What type are you trying to know about? Garage doors uses a fixed beam of light that once you walk past the light it interrupts the beam and electronically sends a signal in the garage door opener to reopen the door.........gl
A motion sensor or pressure pad activates the door, which then usually uses a hydraulic system to open and close the door.
under the point 3.4 others there are some functions listed :) Mostly it is a moving sensor who catches a signal to open and close the door :P
There is a sensor near it. When anyone approaches it detects the person and sends the signal to the doors to open.
